• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.135-143
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• 1990

Based on the mechanism of flat jack used to measure stresses in rocks, a prerssure gauge was developed to measure vertical stresses acting on the rigid boundary in a soil mass. This paper describes the mechanism of the newly built pressure gauge, the process of calibrating the response of this gauge, and its use to centrifugal model tests. By installing this gauge in centrifugal model experiments of reinforced earth retaining walls, vertical stress distribution at the rigid boundary of model wall was obtained and compared with theoretical prediction of trapezoidal vertical stress distribution.

• Geotechnical Engineering
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• v.10 no.2
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• pp.109-120
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• 1994

One of problems being faced during construction of soil structures along the coastal regions is the stabilization of soft clay foundation, In this study, centrifugal model bests were conducted to investigate behavior effect of soft foundation reinforced by cement -soil piles for the stabilization of softs clay foundation during the embankment construction. This paper presents results of settlement and heaving behavior of reinforced and unreinforced foundation with time under the swaged loading for different best conditions. The test results have shown that the reductions of vertical settlement of the foundation and heaving of the ground surface adjacent to the embankment are greatly influenced by strength of improved pile, and moisture content, and especially the ratio of replacement area.

• Journal of the Korean Institute of Navigation
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• v.3 no.1
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• pp.19-28
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• 1979

There are two different assertions on the rolling error in the solid-controlled gyro compass which contains two rotors in its inner gyro sphere. One assertion is that there is a rolling error and the other is that there is no rolling error. This paper examines the rolling error caused by the centrifugal force by the experiment to reveal that the first assertionis reasonable, and it also attempts to explain qualitatively how the rolling error occurs. The Hokushin-Plath gyro compass is chosen as a model. The rolling error is examined by the swing test in various periods. From the tests, the following results are obtained. As long as the swing is continued under the fixed condition of the ship's heading, the swinging period and the amplitude, no error appears. In case the gyro compass is affected by the swingings except those of the cardinal planes, the error starts to appear only after the swing is finished and it is increasing slowly. It takes about 20 minutes for the error to reach its maximum value. The type of this error is a quadrantal one which makes the ship's heading high in the first and third quarters and low in the second and fourth quarters. But in each case the experimental maximum error is greater than the theorectical one.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2355-2364
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• 2018

We evaluated the effect of particle size and associated dynamics on a hydrocyclone separation process in order to understand the movement of the particle trajectories inside the hydrocyclone via numerical analysis, with particles of acid hydrolysis residues discharged in $TiO_2$ production via the sulfate method as a case study. The values obtained from the numerical simulation were successfully compared with those from experimental tests in the literature, allowing a description of the dynamics of the particles, their acting forces, and their relevant properties together with separation efficiency. The results showed that particle motion is jointly controlled by the drag force, the pressure gradient force and the centrifugal force. With increasing particle size, the influence of the drag force is weakened, whereas that of the centrifugal force and pressure gradient is strengthened. Factors including particle density, slurry viscosity, and inlet slurry flow rate also contribute to a clear and useful understanding of particle motion behavior in the hydrocyclone as a method for improving the separation efficiency.

• Geotechnical Engineering
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• v.5 no.3
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• pp.51-62
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• 1989

Prior to the centrifugal model experiments of reinforced earth retaining walls, frictional tests were performed to investigate the frictional behavior between the sand and the reinforcements. Coefficient of friction between the soil and the reinforcements was evaluated using different reinforcements, their lengths and testing methods. Two different testing methods, the direct shear and the pull-out tests, were adopted and their testing results were compared to determine which. method better represented the actual behavior In the field.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.128-138
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• 2022

In this study, in order to apply ultra-high-strength concrete beams of 100 MPa or more manufactured by centrifugal molding as the superstructure of the avalanche tunnel, the purpose is to verify the structural safety of the corner rigid joint in which the centrifugal molded beam is integrated with the substructure, which is the negative moment area. A full-size specimen was manufactured, and loading tests and analysis studies were performed. In order to expect the same effect that the maximum moment occurs in the corner joint part of the upper slab end when the standard model of the avalanche tunnel is designed with a load combination according to the specification, a modified cantilever type structural model specimen was manufactured and the corner rigid joint was fixedly connected. A study was performed to determine the performance of the method and the optimal connection construction method. The test results demonstrated that the proposed connection system outperforms others. Despite having differences in joint connection construction type, stable flexural behavior was shown in all the tested specimens. The proposed method also outperformed the behavior of centrifugally formed beams and upper slabs. The behavior of the corner rigid joint analysis model according to the F.E. analysis showed slightly greater stiffness compared to the results of the experiment, but the overall behavior was almost similar. Therefore, there is no structural problem in the construction of the corner rigid joint between the centrifugally formed beam and the wall developed in this study.

• Magazine of the Korean Society of Agricultural Engineers
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• v.18 no.4
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• pp.4209-4217
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• 1976

The purpose of this thesis is to search for the determination method of pumping rates in the existing tube wells for irrigation. Pumping tests were carried out for the twelve test tube wells which were selected in the provinces of Kyounggi, Kangwon, Chungbuk and Chungnam. The depths, static water levels, pumping levels, drawdowns and yields of tube wells were measured in the pumping tests, and a centrifugal pump with 3 inches diameter, a 5 HP motor and a 90$^{\circ}$ V-notch were used in the pumping tests. The average coefficient of transmissibility calculated by Chow's and Jacob's methods is 0.0336 square meter per second, and the average pumping rate calculated by Thiem's, Smreker's, Brinkhaus' and Theis' formulae, is 919 cubic meter per day, Therefore, the ground water storage in the test areas is comparatively abundant. Correlation between pumping rates and depths of tube wells is not in existence. Also, correlation between pumping rates and the thickness of aquifer is not found in this experiment. This shows that the depths of some tube wells are deep and their thicknesses of aquifer are thick, but their ground water storages are poor, and that the depths of some tube wells are shallow and their thicknesses of aquifer are thin, but their ground water storages are abundant. It seems that the test tube wells are influenced by the peculiar characteristics that the ground water in the test areas is free ground water in alluvium layer closely related with surface water. As drawdown increases, pumping rate decreases, and as the coefficient of transmissibility increases, pumping rate also increases. Namely, there are negative correlation between pumping rate and drawdown, and positive correlation between pumping rate and the coefficient of transmissibility. Judging from the results of the pumping tests in these tests areas, the pumping rate calculated by the formula, {{{{ { Q}_{m } =Q { ( { { S}_{ m} } over { TRIANGLE S } )}^{ { 2} over {3 } } }}}} used traditionally, is likely to be higher than real pumping rates. The formula, {{{{ { Q}_{m } =Q { { H}^{ 2} } over { (2H- TRIANGLE S) TRIANGLE S} }}}} derived from Thiem's theory, is looked upon as the reasonable one to detemine pumping rates in the existing tube wells for irrigation.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.187-193
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• 2001

This paper is results of extensive centrifuge model experiments about design factors influencing the bearing capacity and the settlement behaviors of SCP (Sand Compaction Pile). Centrifuge model tests were carried out changing design factors for SCP method such as replacement area ratio (as= 20, 40, 70%), improvement ratio to footing width (W/B = 1, 2, 3), and amount of fines in sand pile (#200 = 5, 10, 15). Therefore, the effects of these design factors on the bearing capacity and the settlement behavior of SCP were investigated and changes of stress concentratio rato due to such an design factors were also investigated. Centrifuge model testing technique for preparing and installing centrifuge model of sand compaction pile, using freezing them, was also developed. As results of centrifuge model tests, more fines in sand compaction pile increases the bearing capacity of SCP. Optimum improvement ratio to footing width was found to be 2. Values of stress concentration ratio was in the ranges of 1.5 - 3.5. The depth of bulging in sand piles was found in the range of 2.0 - 2.5 times of pile diameter.

• International Journal of Fluid Machinery and Systems
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• v.3 no.3
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• pp.235-244
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• 2010

Recent studies on the moment whirl due to leakage flow in the back shroud clearance of hydro-turbine runners or centrifugal pump impellers are summarized. First, destabilizing effect of leakage flow is discussed for lateral vibrations using simplified models. Then it is extended to the case of whirling motion of an overhung rotor and the criterion for the instability is obtained. The fluid moment caused by a leakage clearance flow between a rotating disk and a stationary casing was obtained by model tests under whirling and precession motion of the disk. It is shown that the whirl moment always destabilizes the whirl motion of the overhung rotor while the precession moment destabilizes the precession only when the precession speed is less than half the rotor speed. Then vibration analyses considering both whirl and precession are made by using the hydrodynamic moments determined by the model tests. For larger overhung rotors, the whirl moment is more important and cause whirl instability at all rotor speed. On the other hand, for smaller overhung rotors, the precession moment is more important and cancels the destabilizing effect of the whirl moment.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.979-990
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• 2010

Although a centrifuge model test is performed with scaled models, it has a lot of advantages compared with usual scale model tests, for the reproduction of stress levels equal to a full scale test is possible. At the beginning of the Daewoo Institute of Construction Technology, a servo-motor-driven single axis actuator was introduced and has been in use with a geo-centrifuge. However, for variety of experiments and construction stage simulation, various apparatuses have been developed, such as a vacuum generator, a lateral actuator for tidal power simulation, a gravel hopper and a sand drainer for filled-up ground, and a water level controller. The apparatuses have been manufactured with enough strength and durability to be operated under specific g levels. This paper presents the properties of the apparatuses and the results of the tests performed with those.